Implantation occurs anywhere from 6-12DPO and its not until then that hcg starts getting produced. Apparently its the hcg that causes the M/S. My thoughts are its unlikely that its M/S at this stage - if there's not enough hcg in your system to give a BFP then there's probably not enough to give you M/S. Do you ever get nausea in your normal LP? I used to get nausea on and off from 9DPO until AF (likely progesterone related).

Having said that I've heard plenty of stories of women getting pg symptoms including M/S from very early on. I really hope its a BFP for you! Good luck